The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the Fluxgit MCP Server listing page.
mcp-name: io.github.fluxgit-hq/fluxgit-mcp-server
Safety-first Model Context Protocol (MCP) server for Git.
AI agents inspect. FluxGit keeps control.
A Rust MCP server with 38 contracts for AI code agents: 25 read-only tools and 13 human-gated operation tools (12 proposals plus cancellation of a pending proposal). The sidecar never executes a Git write; it bridges approved proposals to the FluxGit desktop application.

For context-budget comparisons, see the public Git context token benchmark. It publishes the fixture, raw outputs, scripts and checksums, including both the broad CLI sweep and a smaller hand-tuned counterexample.
AI coding agents are increasingly asked to navigate real repositories: explain branch state, summarize diffs, find lost commits, recommend safe next steps. To do this well, an agent needs Git context that is richer than git status and structured enough to reason over. To do this safely, an agent must never be able to silently mutate refs, force-push, discard work, or apply patches without a human approving the consequence.
Other MCP Git servers face a choice: stay strictly read-only (limited utility) or expose write tools directly (dangerous — agents hallucinate, prompts can be poisoned, mistakes are destructive). This sidecar chooses neither. Inspection is schema-validated and bounded; operations go through a write-with-UI-handshake: the agent proposes, FluxGit shows the preview, the user approves in the app, and FluxGit executes through its safety pipeline with restore points and audit.
| Tool | Purpose |
|---|---|
repo.brief | One-call situational awareness — branch, ahead/behind, in-progress operation, working-tree summary, stashes, aggregated submodule drift, recent commits, detected conventions and next-step hints. The recommended first call of an agent session; replaces 6-10 raw git calls and is token-budgeted by design |
repo.scope | Monorepo scoping — one subtree's working-tree changes, recent commits, churn (commits + authors over a window) and CODEOWNERS owners in a single call |
repo.status | Working tree, current branch, dirty paths |
repo.refs | Branches, tags, remotes, stashes |
repo.branchStack | Current branch vs upstream / base / related |
repo.history | Paginated commit history |
repo.reflog | Movement timeline with recovery hints |
repo.conflictPreflight | Predict merge/rebase outcome before running |
conflict.read | Active conflict as structured data — in-progress operation, ours/theirs producing commits, per-file stage classification, base/ours/theirs contents (size-capped, binary-flagged) and marker region line ranges. No more parsing <<<<<<< soup |
commit.details | Single commit metadata + changed files |
worktree.changes | Per-path working tree change summary |
worktree.list | All worktrees (main + linked) with branch/detached, HEAD SHA and locked/prunable flags — the read-only base for parallel agent worktrees |
submodule.status | Submodule list and state |
diff.text | Standard text patch (git diff compatible) |
diff.semantic | Capability-negotiated semantic explanation |
diff.semanticFallbacks | Paths that fell back from semantic to text |
fleet.radar | Multi-repo attention queue |
fleet.digest | What changed across the fleet since a time — HEAD and local-branch reflog moves of many repositories, newest first, bounded by maxEvents (default 200, max 1000). repoPaths, or FluxGit's registered repositories inside the allowed roots when omitted. identity is exactly what Git recorded (the configured identity, not proof of a person or an agent); rewrote flags moves that dropped the previous tip (reset, amend, rebase, forced moves). Reads reflog files only; nothing is fetched or written |
agents.presence | Which other coding agents are working in this repository — from local sources only (running agent processes and their children, the agents' own session stores, files they keep in the repository, editors with built-in agents, and FluxGit MCP presence records). Per agent: state (working/open/recent), sources, branch, last tool and repository-relative files when known. Names are what each tool or MCP client declares about itself. Your own MCP record is excluded; findings that are probably your own session are marked likelyCaller. Never returns prompts, messages or file contents |
safety.timeline | Synthesized safety events from restore points + reflog |
safety.eventDetails | Drill-down into one timeline event |
flux.latestRestorePoint | Newest FluxGit restore point |
flux.restorePoints | List of restore points |
flux.restorePointDetails | One restore point with before/after refs |
operation.status | Authoritative asynchronous status by previewId; poll after a preview returns accepted: true and do not report a Git outcome before it becomes terminal |
All 12 operation.preview.* proposals dispatch through the FluxGit gateway when
configured. The sidecar POSTs the proposal, performs one bounded status read,
and normally returns immediately with accepted: true, the canonical
previewId, current status and nextAction.tool: "operation.status". The
FluxGit app renders a “Requested by AI agent” approval card while human review
continues asynchronously. Code 10003 is reserved for a bridge that is absent,
invalid or unreachable; it is not a human-approval timeout.
All 12 preview schemas accept an optional bounded idempotencyKey. Reuse it
only when retrying the same logical intent; the sidecar scopes it to the
operation type so that retry resolves to the existing gateway proposal. Omit
it for a new intent—even when the other arguments match—and the sidecar sends
a fresh UUID-backed key. Preview tools therefore continue to advertise
idempotentHint: false.
| Tool | Purpose | Gateway dispatch |
|---|---|---|
operation.preview.merge | Propose a merge for human review | POST /v1/mcp/operation/preview/merge → approval card in FluxGit |
operation.preview.rebase | Propose a non-interactive rebase | interactive: true fails schema validation before POST/card creation; accepted requests POST /v1/mcp/operation/preview/rebase and open a rewrites-history warning card |
operation.preview.discard | Propose discarding working-tree changes | POST /v1/mcp/operation/preview/discard → path-specific warning; FluxGit requires a safety stash before it discards matching changes |
operation.preview.reset | Propose soft / mixed / hard reset | POST /v1/mcp/operation/preview/reset → mode-aware card (hard mode forces strong confirmation) |
operation.preview.patch | Propose applying an agent-generated patch | POST /v1/mcp/operation/preview/patch → monospace patch preview + applyToIndex toggle |
operation.preview.plan | Propose a 1-10 step sequence using the five supported plan-step types (merge, rebase, discard, reset, patch) | POST /v1/mcp/operation/preview/plan → numbered step card; destructive steps require an explicit checkbox. A rebase step with interactive: true is rejected by schema validation before dispatch; execution stops at the first failure. Its pre-plan checkpoint anchors only the branch commit: guarded recovery restores HEAD/tracked files, while the original index, working tree and untracked files require the separate step snapshots/Safety Timeline recovery surfaces |
operation.preview.worktree | Propose creating an isolated worktree for a parallel task (non-destructive; never touches history) | POST /v1/mcp/operation/preview/worktree → approval card with branch + target path + reason; runs through the same worktree-create action a manual click uses |
operation.preview.commit | Propose staging + committing with a message (non-destructive; amend not supported) | POST /v1/mcp/operation/preview/commit → approval card lists the exact files that will be staged and committed; runs through the normal commit pipeline (hooks, signing, policy); completion returns the new SHA |
operation.preview.push | Propose pushing a branch to a remote (optional set-upstream; force-with-lease shows a HIGH-risk warning) | POST /v1/mcp/operation/preview/push → approval card with remote + branch + force warning when applicable; runs the guarded push flow |
operation.preview.branch | Propose creating (and optionally checking out) a branch from a start point | POST /v1/mcp/operation/preview/branch → approval card with name + start point + checkout choice |
operation.preview.branchDelete | Propose deleting merged local branches in one or more repositories (targets, up to 20 repositories × 20 branches, 100 in total). The agent names branches; FluxGit decides which are deletable. Remote branches are never touched | POST /v1/mcp/operation/preview/branchDelete → the card inspects every branch natively and keeps any branch with commits not in HEAD or its upstream, checked out anywhere, or whose tip moved; each deleted tip is journaled in the Fleet branch-deletion history, where Restore recreates it. Completion returns per-branch deleted/failed/skipped results |
operation.preview.submodulePointer | Propose recording (record, requires message) or returning to (return) one submodule pointer at any depth (parentPath + relativePath). Optional expectedRecordedOid / expectedCheckedOutOid pins, as read from submodule.status | POST /v1/mcp/operation/preview/submodulePointer → record commits only the gitlink in the parent through Git's own commit (hooks and signing apply; nothing is pushed); return checks out the recorded commit detached, journaling the previous checkout as a restore point. The submodule must be initialized, clean and differ from its recorded pointer |
operation.cancel | Cancel the agent's own still-pending proposal by previewId | POST cancel; the card disappears from the user's queue like an expired proposal |
All write proposals require a free-text reason so the user sees the agent's justification in the approval modal. All reuse the same durable gateway lifecycle (pending → approved → executing → completed|failed, with rejection/cancellation/expiry branches) and the same Tauri bridge in the UI. Six shims cover pending, recoverable, approve, claim, reject and complete. After restart, Approved proposals may resume only after repo/ref revalidation and claim; Executing proposals are shown for explicit reconciliation and are never blindly re-executed. When an approved operation captures a restore point, the completion result exposes that recovery metadata so the agent can report it without guessing.
The boundary is deliberately fail-closed at approval time. FluxGit resolves the
proposal's repoPath to its canonical open-repository id and requires it to
match the repository the human is reviewing; an unresolved path, mismatch, or
repository switch blocks execution. Tool arguments are validated before
dispatch and again by the gateway. An optional declarative agent policy can
deny proposals before a card opens. Its rules match the agentId the sidecar
forwards (the sanitized, self-declared clientInfo.name, such as claude-code)
and can limit that agent to operations, refs and, with pathConstraints,
repository and worktree path prefixes. If FLUXGIT_MCP_AGENT_POLICY is configured
but the file is missing, unreadable, malformed, or unsupported, the gateway
does not start. With no configured policy, compatibility remains permissive,
but per-operation human approval is still mandatory.
Every operation.preview.* result may carry an optional otherAgents object:
the other agents agents.presence finds in the proposal's repository and, when
both sides name their files (discard and commit paths, patch headers, plan
steps, the submodule directory of submodulePointer), the overlappingPaths. It is informational only: it is added after
the gateway decided, never blocks a proposal and never changes how it is
approved. It is absent when agent detection is disabled.
Detection is local and read-only: other agents' SQLite stores are opened
read-only and only repository-relative paths, tool names, branches and times
leave the detector. FLUXGIT_MCP_AGENT_DETECTION_DISABLED (any value) turns it
off: agents.presence then returns 10011 and previews carry no hint.
Each sidecar also records which repositories its client used, so the desktop
and other sidecars can see it: <run_dir>/presence/mcp/<pid>.json (0600) with
the self-declared clientInfo name and version and, per repository, the
canonical path, time and last tool name. Only calls that were accepted are
recorded (a proposal the agent policy or a missing FluxGit refused is not);
the file is removed on clean exit. FLUXGIT_MCP_PRESENCE_DISABLED turns it
off.
Every operation.preview.* call follows the same wire protocol. Example for operation.preview.merge:
1. Sidecar POSTs the proposal:
2. Gateway responds 202 Accepted:
3. Sidecar performs one bounded status read:
If the proposal is still live, the preview tool returns promptly:
This is a successful proposal submission, not a successful Git operation.
4. Client polls operation.status until the gateway reports a terminal state:
completed returns isError: false. A live pending or approved proposal
also returns as a successful accepted result, but it does not claim Git changed.
Any non-completed terminal state (rejected, failed, expired, cancelled)
returns isError: true with the structured payload, so the agent can report the
real outcome instead of inventing one.
The same pattern applies to all 12 operation.preview.* tools. Only the request
body fields and result shape differ; proposal submission, the one immediate
read, asynchronous operation.status continuation and error semantics are
shared. The public contract summary is maintained at
fluxgit.com/features/mcp-agent-git.
The sidecar speaks MCP without FluxGit installed. Standard Git inspection works (status, refs, history, reflog, diff.text, etc). The tools that require FluxGit return JSON-RPC error code 10001 with an upgradeHint pointing the agent at the install/configure flow.
Tier classification:
git only: repo.brief, repo.scope, repo.status, repo.refs, repo.branchStack, repo.history, repo.reflog, commit.details, worktree.changes, worktree.list, submodule.status, diff.text, conflict.read, fleet.digest. agents.presence also needs no FluxGit: it reads local agent state (and FluxGit's MCP presence records when present).fleet.radar, diff.semantic, diff.semanticFallbacks, repo.conflictPreflight.gateway_not_configured without FluxGit because synthesizing them from local refs alone would mislead the agent: safety.timeline, safety.eventDetails, flux.latestRestorePoint, flux.restorePoints, flux.restorePointDetails.operation.preview.* tools return an accepted live
proposal promptly and continue through operation.status; operation.cancel
withdraws a pending proposal owned by the same agent. Code 10003 is used
only when the bridge cannot accept or serve the handshake.Install the published crate (puts fluxgit-mcp-sidecar on your PATH):
To install the current source branch instead:
Or build from a clone:
Paste the generic block below into any MCP host config. No client-specific install required.
FLUXGIT_MCP_HANDSHAKE_ADDR is the canonical bridge address generated by
FluxGit Quick Connect. FLUXGIT_GATEWAY_ADDR and FLUXGIT_GATEWAY_URL remain
compatibility fallbacks. The sidecar accepts only plain HTTP on a loopback host
with an explicit port; a remote host, credentials, path, query, fragment, HTTPS,
or missing port is rejected. Without a valid local bridge, the free-shell tier
still works.
FLUXGIT_MCP_AUDIT_LOG enables an append-only JSONL audit log of every tools/call. Arguments are hashed; raw paths and identifiers are never written verbatim.
diff.semantic is the most-used tool for AI agents and the easiest to misuse. The rule is strict:
A result may only be called semantic if
data.supportedis exactlytrue.
When the FluxGit semantic engine is not available (FluxGit app not running, gateway address not configured, or the repository not registered in FluxGit), diff.semantic returns:
With the FluxGit app running and the repository registered in FluxGit, the same call is served by the FluxGit diff-engine through the gateway's read-only bridge and returns supported: true with per-file semantic hunks:
Honesty is per file, not just per call: files the engine could not parse arrive with fallbackToText: true, a reason, and ready-to-use textDiffArguments — never as synthesized semantic hunks. diff.semanticFallbacks follows the same split and, when connected, lists the engine's real per-file fallback records.
Connected agents must:
diff.semantic.data.supported.true, use the semantic payload and label results as semantic — except entries with fallbackToText: true, which must be presented as text fallbacks.false, call diff.text with data.textDiffArguments and present results as a text-diff fallback.Allowed wording: "FluxGit reported a text-diff fallback for this file".
Prohibited wording: "This is a semantic diff" when supported=false.
Unless FLUXGIT_MCP_PRESENCE_DISABLED is set, each sidecar process keeps one
local file, <FluxGit run dir>/presence/mcp/<pid>.json, so the FluxGit desktop
app can show which coding agent is connected and which repository it is working
on. It holds only the client name and version the agent declared in
initialize, and per repository (at most 16) the checked repoPath, the time
of the last call and the tool name. No other arguments, no results. Unlike the
audit log, the repository path is stored as-is so the desktop can match it; the
file is private (0600 in a 0700 directory), rewritten atomically, deleted on
clean exit, swept after 24 hours, and writing it never affects a tool call.
The client name is self-declared, not an authenticated identity.
Unless FLUXGIT_MCP_AUDIT_DISABLED is set, the sidecar attempts to append each
tools/call to the shared JSONL ledger. The gateway attempts human-decision
appends through the same writer. FLUXGIT_MCP_AUDIT_LOG overrides the path;
otherwise both processes use <FluxGit run dir>/audit/mcp.jsonl (including
FLUXGIT_RUN_DIR):
Sensitive paths and identifiers are hashed, never stored verbatim. One stable cross-process lock protects validation, rotation and the complete append plus sync. Lines are limited to 256 KiB. The active segment rotates at 4 MiB and at most four rotated segments are retained, with a signed checkpoint when signing is configured.
Audit signing is opt-in. When FLUXGIT_MCP_AUDIT_SIGN_KEY points to a PEM PKCS8 Ed25519 private key, every appended entry is signed with that key. Signed entries add:
signature — base64url (no padding) Ed25519 signature over the canonical JSON of the entry without the signature field.signatureKeyId — 16-char hex prefix of the matching public key, so rotated keys can co-exist in the same JSONL.signatureVersion: 3 — current chained signing domain; the key id, sequence,
previous hash and entry hash are included in the signed bytes.Canonical JSON rule (verifier must match exactly): recursively sort every
object's keys lexicographically by UTF-8 byte order; arrays preserve order;
strip signature; serialize compactly. For versions 2 and 3, keep
signatureKeyId and signatureVersion in the signed object. For legacy signed
entries with no version, the verifier also strips signatureKeyId.
If the env var is unset, new entries are chained but unsigned for backward compatibility. If it is explicitly set, an empty, missing, unsafe, oversized or invalid key fails audit startup closed; it never degrades to unsigned output.
The sidecar binary doubles as a verifier:
The CLI streams the active file and retained rotations with bounded memory. It
validates sequence, hashes, segment names, checkpoints and signatures, then
reports only bounded counters (entries, chained, legacy, signed,
unsigned, segments and the retained sequence range). Legacy per-entry
records remain readable and verifiable but are reported as legacy, never as
part of the tamper-evident chain. For a strict evidence gate, run:
Exit code is 0 on success, 3 for malformed data, broken chain/rotation, a
bad signature and, in strict mode, any unsigned entry; usage errors return 2.
Programmatic full-ledger verification uses verify_audit_ledger; the older
verify_audit_event_signature remains available for compatible per-entry
checks. A local chain cannot prove deletion or replacement of the entire
retained history (or its local checkpoint) without an independently trusted
external anchor. Signed retained entries do prevent an attacker without the
private key from recomputing a modified chain.
Audit configuration (including an explicit signing key) fails closed at startup. A later filesystem/full-disk append failure is logged as degraded but does not undo a tool response or an already-durable gateway lifecycle transition; the gateway lifecycle journal remains authoritative for recovery.
The server supports two protocol eras:
2026-07-28 (preferred, stateless): call server/discover, then include
params._meta.io.modelcontextprotocol/protocolVersion and
params._meta.io.modelcontextprotocol/clientCapabilities on every request.
Modern results carry resultType: "complete" and server metadata; list
results add ttlMs and cacheScope. tools/list includes title,
inputSchema, outputSchema and annotations. tools/call includes both
presentational content and the same payload in structuredContent.
Only the proposal tools and operation.status advertise previewId,
status, accepted and nextAction in their outputSchema; schema
objects are open unless they say "additionalProperties": false.2024-11-05 (legacy compatibility): older hosts continue to use
initialize. Modern-only fields are omitted from legacy results.Stdio output is standard newline-delimited JSON-RPC 2.0: exactly one compact
JSON value per line. The JSON in a result's content[0].text is compact too
(no indentation), with the same keys and values as structuredContent. Pre-standard Content-Length framing remains accepted as
input only for old FluxGit clients; the server never emits it. Frames are
limited to 8 MiB. JSON-RPC notifications receive no response, and request
methods sent without an id are not executed.
There are 38 tools in modern tools/list: 25 advertise
annotations.readOnlyHint: true; the 12 operation.preview.* tools and
operation.cancel advertise readOnlyHint: false. These annotations describe
effects for the host; they are not authorization.
Error codes:
| Code | Meaning |
|---|---|
-32700 | Parse error |
-32600 | Invalid request (malformed JSON-RPC) |
-32601 | Method not found |
-32602 | Invalid params or unknown tool |
-32603 | Internal error |
-32022 | Unsupported modern MCP version; data contains supported and requested |
10001 | Gateway not configured — install/start FluxGit to use FluxGit-required tools |
10002 | A configured FluxGit bridge had no payload to serve (for example, a local fallback lacked an absolute repoPath) |
10003 | The local write-handshake bridge is absent, invalid or unreachable; no accepted proposal should be inferred |
10004 | Proposal ended without completion (rejected, failed, expired or cancelled) |
10005 | The gateway does not know the requested previewId (wrong/never-accepted id or pruning after terminal retention). Restart alone does not justify a new proposal: Approved/Executing records recover durably and a possibly-started Git outcome must be reconciled first. |
10006 | Gateway refused the proposal before opening a card (policy, validation or quota) |
10007 | Gateway returned a malformed/unsafe canonical previewId; the sidecar refuses to follow it |
10010 | Local read-only Git command failed |
10011 | Agent detection is disabled (FLUXGIT_MCP_AGENT_DETECTION_DISABLED); agents.presence cannot answer |
This is a working MCP server. The read-only surface and all 12
operation.preview.* routes are implemented; operation.cancel manages only a
pending proposal owned by the same self-reported agent id. The write handshake
renders an approval card in FluxGit and completes through the app's guarded
pipeline. Clients receive structured lifecycle results instead of a synthetic
success. clientInfo.name is sanitized attribution for policy, quota and audit;
it is self-reported and must never be treated as authenticated identity.
io.github.fluxgit-hq/fluxgit-mcp-server is live and resolves to the published fluxgit-mcp-sidecar crate.Apache-2.0. See LICENSE.